14 
intervals of time and the photographs were taken with an open stereo- 
camera. Otherwise the room was of course dark. The wandering of the 
particles appear very clearly at stereoscopic viewing of the photographs 
and the measuring is easily done. As the photographs were taken through 
glass into the water a certain calibrating of the measurements had to be 
done by taking photographs of objects with known dimensions through 
the glass and water. Tc determine the speed of currents cf air, very light 
objects as bubbles of plast were sent up in the currents and were lighted 
up by a stroboscope in front of an open stereo-camera. The speed and 
direction of the current of air could then be determined as above. The 
same technique was used for certain medical purposes when studying 
movements of the body e. g. the movements of the foot in normal walk. 
Some Investigations concerning Photogrammetry in Medicine. 
Determination of Swellings. 
All measurements on the soft human body are difficult to perform with 
high accuracy, if such measuring device and methods are used as may 
deform the surface. Photogrammetry has appeared to be useful in such 
cases and has been used for research purposes to determine variations of 
the dimensions of fingers and tc investigate the development of swellings 
in the face at dental operations. 
  
Fig. 4. Camera arrangement for photogrammetric deter- 
mination of swellings of fingers. 
In the first case (publication No. 1) the fingers were photographed with 
two sterec-cameras as shows fig. No. 4. The photographs must be taken 
by flash-light to eliminate the problem of synchronizing the shutters with 
sufficient accuracy. The stereocomparator was used tc measure the dimen- 
sions of the fingers. From diametrically opposed points on the surface of 
the finger the distances between the edges of the two rulers were deter- 
mined. As the breadth of the rulers was known it was then easy to calculate 
the thickness of the finger. By taking photographs of the finger under 
   
  
   
  
  
   
  
   
   
   
   
   
   
   
    
   
  
  
  
  
  
  
   
  
   
  
  
  
   
  
  
  
  
  
  
  
   
  
   
  
   
    
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